It marked the earliest exit of a top seed in this tournament since Haas lost in the first round to Teymuraz Gabashvili in 2010. The No. 1 seed has claimed the Delray Beach title only once in the tournament's 22-year history.

Johnson, ranked No. 142 in the world, needed to win two qualifying matches to gain entry into the main draw of the 32-player field.

"I've had a few wins I'll never forget, and this is one of them," said Johnson, a two-time NCAA champion at USC.

Johnson, who turned pro in 2012, will next face No. 6 seed Feliciano Lopez of Spain. Johnson had 13 aces in his win against the 35-year-old Haas, who is ranked No. 12 in the world.

"I hate to lose, but I'm happy for him," Haas said.

Lopez needed three sets to move to the next round earlier Wednesday. He rallied to defeat Adrian Mannarino 4-6, 6-4, 6-2.

Kevin Anderson and Marin Cilic also advanced on Wednesday.

Anderson, the No. 4 seed, reached the quarterfinals when Ivo Karlovic retired because of a stomach ailment after Anderson won the first game. Karlovic was a finalist in Memphis last week.

Cilic, the No. 7 seed, made easy work of Benjamin Becker, taking only 55 minutes to win 6-1, 6-3 in a first-round match. Cilic has won 14 of his 18 matches this season.

The most surprising result of the afternoon occurred in a first-round doubles match when Sekou Bangoura and Vahid Mirzadeh of the United States upset No. 2 seed Eric Butorac and Raven Klaasen 7-5, 3-6, 10-5 after learning on Tuesday they would be in the tournament as an alternate.

"The other day I was giving lessons, and now I'm here," said the 27-year-old Mirzadeh, who lives a short distance away in Wellington, Fla. "A win like this lifts your spirits and shows that maybe I can compete at this level."